The present invention relates to an insulation-piercing connector including a piercing block for receiving a cable inserted therein and a terminal block having therein piercing terminals adapted to pierce the cable so as to accomplish electrical connection therebetween when the piercing and terminal blocks are forced closer together.
One example of conventional insulation-piercing connectors is shown in a perspective view of FIG. 6 and sectional views of FIGS. 7a and 7b for explanatorily illustrating the construction of the connector and its insulation-piercing connection. The insulation-piercing connector 1 is composed of a terminal block 2 and a piercing block 3. The terminal block 2 is formed with a plurality of connection apertures 4 for receiving contacts of a male connector (not shown) to be connected to the connector 1 and is provided with L-shaped piercing terminals 6 fitted in terminal grooves 5 communicating with the connection apertures 4. Each of the L-shaped piercing terminals 6 has a U-shaped grooved portion 6a to be fitted in the terminal grooves 5 to form a contact portion to be connected with one of contacts of the male connector (not shown). Each of the piercing terminals 6 has also a vertical portion 6b which is formed with a V-shaped piercing groove 6c into which an insulated wire 7 of a cable is press-fitted.
The piercing block 3 is pivotally connected to the terminal block 2 by means of a hinge 8 generally integrally formed with both the blocks 2 and 3. The piercing block 3 is formed with wire receiving apertures 9 passing therethrough in the connecting direction of the connector 1. The insulated wires 7 of the cable received in the apertures 9 are pierced with inner edges of the piercing grooves 6c to electrically connect the wires 7 to the piercing terminals 6 when the terminal block 2 and the piercing block 3 are forced closer together.
"To force blocks closer together" used herein means that the blocks are forced toward each other to form a united body.
The piercing block 3 is formed with V-shaped grooves 10 at the respective ends of the wire receiving apertures 9 on the side where the forward ends of the insulated wires 7 project from the piercing block 3 after inserted through the apertures 9. The V-shaped grooves 10 embrace or hold at their bottoms the ends of the insulated wires 7 in curved state after the forward ends of the insulated wires 7 projecting from the apertures 9 have been bent upwards. The piercing block 3 is further formed with receiving openings 11 substantially perpendicular to the wire receiving apertures 9 for receiving the distal ends of the vertical portions 6b of the piercing terminals 6, respectively.
In piercing the cable in the connector 1, the insulated wires 7 of the cable are inserted in the direction shown by an arrow E in FIG. 7a into the wire receiving apertures 9 of the piercing block 3 in an open condition where the piercing block 3 has been pivoted about the hinge 8 relative to the terminal block 2 from the closed condition shown in FIG. 6. The forward ends of the insulated wires 7 projecting from the apertures 9 are then bent upwards so as to hold the bent portions of the wires 7 by means of the bottoms of the V-shaped grooves 10. In this state, extra portions of the insulated wires 7 projecting from the grooves 10 are cut off along a dot-and-dash line 12 in FIG. 7a by means of cutting means such as pliers (not shown). Therefore, conductors of the insulated wires of the cable appear at their cut ends, which make it possible to ascertain in continuity test whether the plurality of conductors have been connected in position to the piercing terminals 6 in an intended fashion without any wrong connection therebetween.
After completion of the continuity test, the terminal and piercing blocks 2 and 3 are forced closer together to join them as shown in FIG. 7b. In the joining operation, the respective insulated wires 7 of the cable received in the wire receiving grooves 9 are pierced with the inner edges of the V-shaped piercing grooves 6c so that the inner edges of the grooves 6c pass through insulators of the wires 7 and penetrate into the conductors, thereby electrically connecting the conductors of the insulated wires 7 to the piercing terminals 6, respectively. FIG. 6 illustrates in a perspective view the insulation-piercing connector 1 whose piercing terminals 6 have been connected to the conductors of the cable.
In such a connector of the prior art described above, insulated wires 7 of a cable are inserted and supported in the wire receiving apertures 9 and the forward ends of the wires 7 are then bent upwards so as to be held by the inner walls of the V-shaped grooves 10 at the ends of the apertures 9, thereby enabling the extra portions projecting from the grooves 10 to be cut off by means of cutting means such as pliers. However, since the inner walls of the V-shaped grooves 10 open progressively widely or away from each other towards the outside of the grooves 10, the wires cannot be sufficiently securely held by the grooves 10. Particularly, with a cable having twisted wires, there is a tendency of the wires to come out of the V-shaped grooves 10 owing to the restoring force of the wires returning to their original straight positions. As a result, cut ends of the wires direct in lateral directions at random.
In continuity test, therefore, it may be difficult, if not impossible, to bring one end of a probe for the continuity test into contact with wires of the cable due to the laterally directing cut ends of the wires, which also make it difficult to perform the continuity test itself.
In case of a continuity test of circuits for an appliance such as a switchboard whose male connector has been connected to the insulation-piercing connector 1, an operator cannot clearly see from above the cut ends of insulated wires 7 of the cable of the connector because of the cut ends directing laterally at random. Accordingly, the continuity test must be carried out in an undesirable condition and become more difficult for the operator depending upon the connected state of the insulation-piercing connector 1.